1. Field of the Invention
The present invention generally relates to an electronic endoscope apparatus for acquiring medical information within a biological body by employing a solid-state imaging element or a camera tube. More specifically, the present invention is directed to an electronic endoscope apparatus capable of displaying as an image or numerical data, functional information and shapes of, for instance, a mucous membrane of a stomach, e.g., a concentration of hemoglobin and oxygen saturation of hemoglobin.
2. Description of the Related Art
In a conventional electronic endoscope apparatus, the functional information of a biological body, such as mucous membrane of a stomach, may be observed by firstly photographing the biological body with a plurality of monochromatic lights having different wavelengths so as to acquire a plurality of images thereof. Then, differences between a plurality of absorbances with respect to the monochromatic light having the different wavelengths are calculated from the acquired image information.
In the absorption spectrum curve of, for instance, the concentration of hemoglobin under the mucous membrane as illustrated in FIG. 1, it is known from, e.g., Journal of Biological chemistry, vol. 227 issued in 1957, page 285, that the concentration of hemoglobin is directly proportional to a difference of the absorbance denoted by "C", which is plotted at two different wavelengths of 569 nm (nano meters) and 650 nm. Similarly as is known in this field, the oxygen saturation of hemoglobin is directly proportional to an amount calculated from a ratio of A to B (A/B). As a result, the differences in the absorbances measured at four wavelengths of 569, 577, 586 and 650 nm are calculated and then processed, so that the concentration of the hemoglobin under the mucous membrane, or oxygen saturation of hemoglobin, may be displayed as an image.
As previously described in the conventional electronic endoscope apparatus, functional information can be observed by irradiating the monochromatic light having four different wavelengths to the mucous membrane in order to acquire four sets of the monochromatic light images, by performing a predetermined calculation for these monochromatic light images so as to obtain the concentration of hemoglobin under the mucous membrane and also the oxygen saturation of hemoglobin as the functional information, and by displaying the resultant data as the images. Accordingly, the above-described functional information can be imaged. To obtain such a functional information of the biological body, the external memories, e.g., magnetic tapes and floppy disks are utilized and the data processing is carried out by the off-line process.
In the conventional electronic endoscope apparatus, on the other hand, the acquired functional information is displayed either as the monochromatic image, or the so-called "quasi-colored image" by allocating the R, G, B signals to the functions of the functional information without introducing the definite color allocation basis.
As a consequence, the conventional electronic endoscope apparatus have the following drawbacks.
First, the functional information of the biological body to be examined is once stored into the external memory devices. Thereafter, the functional information data stored in the external memory devices are read and calculated. Then, the acquired functional information is displayed on the display unit of the conventional electronic endoscope apparatus. As a result, such a functional information cannot be provided in a real time for the diagnostic purpose.
Since the image data obtained by using the monochromatic light are stored in the memory device having the large memory capacity which is originally used for storing the color image data of the biological body, a large number of the memory device having the large memory capacity is required for storing both the color image data and monochromatic light image data, resulting in the high-cost endoscope apparatus.
Moreover, when the functional information of the biological body to be examined is displayed as the monochromatic (black/white) image, such a black/white image is not visible for an operator in the conventional electronic endoscope apparatus. Also according to a so-called "quasi-colored imaging method" where the R.G.B. signals are arbitrarily allocated to the various functions of the functional information. Namely, there is no definite rule to allocate the R,G,B signals. In addition, there is no linear relationship between changes in the concentration of hemoglobin under the mucous membrane as the functional information and changes in the hue of the displayed image thereof. As a consequence, it is very difficult to correctly grasp the functional information of the mucous membrane under examination from the displayed quasi-colored images in the conventional electronic endoscope apparatus.